Best practice: Process development for a packaging specialist for PCR processing From PE-LD film flakes to recycled pellets
© DF.FotografieA specialist for packaging and filling systems as well as process technology in the food industry asked IKV for support in process optimisation for the processing of PCR film flakes made of low-density polyethylene (PE-LD) into regranulates. The challenges in regranulation were the fluctuating material properties and compositions of the flake fractions from the post-consumer waste stream, as well as the low bulk density of the film flakes. The system configurations used for the tests reflected the client’s technical conditions and possibilities.
Identification of a suitable plant configuration
IKV developed a system configuration for the compounding and regranulation of PCR film flakes made of low-density polyethylene (PE-LD). The core component was a co-rotating twin-screw extruder. All components and parameters were matched to the company’s existing systems and technical conditions.
The following components were configured and specified for processing the film flakes:
- Screw configuration
- Housing structure
- Addition location of the components
IKV optimized the screw configuration for a twin-screw extruder with eleven temperature control zones that can be heated and cooled individually. The presented sequence and length of different dispersive mixing zones, kneading elements and tooth mixing elements ensures the efficient, optimal material and thermal homogenization of the melt
Compounding tests
The following steps were investigated and optimized in compounding trials:
- Pre-drying: IKV identified suitable time and temperature windows for drying with hot air dryers.
- Dosing: Development of a solution for challenging feeding behavior of the flake material:
- Low bulk density means that the maximum throughput is limited by the free volume in the feed area.
- Due to the nature of the flakes, the material tends to form bridges in the feed area, which can cause the process to stop.
- Pelletizing: Investigation of the effect of feed variations on pellet quality
IKV developed options for optimizing the dosing process and determined a process window for the subsequent production of recycled pellets from various types of film flakes using the screw speed and temperature profile of the screw zones.
Processing of different flake types
IKV processed five different film flake fractions, which were provided by the client, into regranulates. The fractions differed primarily in terms of color composition and the type of pre-treatment (hot/cold wash).
The effects of the input material on the compound quality were determined and documented under uniform processing conditions. IKV produced pilot plant quantities of the granules and made them available to the client for further investigation and processing trials.
Process window analysis for processing behaviour
In a follow-up project, IKV will analyze the processing behavior of the film flakes as a function of the selected process parameters. In addition, the optimization of dosing is being implemented and further investigated in the IKV pilot plant.
Dr.-Ing. Lisa Leuchtenberger-Engel
Head of the Extrusion and Rubber Technology Department
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